This invention relates to crosspoint-type switching networks for communication systems, particularly those networks adapted to use optical switching crosspoints.
Several proposals have previously been made for optical equivalents of more conventional switching apparatus and networks. Some earlier work in this field may be represented by the article by H. F. Taylor, "Optical Waveguide Connecting Network,"Electronics Letters (G.B.), Volume 10, page 41, Feb. 21, 1974. The Taylor reference asserts that techniques for crossing one optical channel waveguide above another and for effectively supplying a switching crosspoint therebetween have not been proposed and have not been demonstrated. The alternatives, as described by the Taylor reference, become extremely cumbersome. In some of the other prior art references, such as U.S. Pat. No. 3,622,792, the optical beams are freely propagating during the switching operation. In another attempt to solve the problem, U.S. Pat. No. 3,871,743, optical fiber waveguides are made to intersect a second set of guides in the switching matrix. The mechanics of aligning such arrangements in a large matrix are difficult.
It would be desirable to provide a more versatile, less problem-prone system than any of those of the prior art.